Non-Hermitian topological physics have attracted much attention[1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}, [9]}, [10]}, [11]}, [12]}, [13]}, [14]}, [15]}, [16]}, [17]}.
In non-Hermitian systems eigenvalues and eigenfunctions are complex in
general. However, they are restricted to be real if \(PT\)  symmetry is imposed[1]}, [19]}, [20]}, [21]}, [22]}, [6]}, [24]}. There is a \(PT\)  symmetry
breaking transition, where the eigenvalues and eigenfunctions become
complex. Nonreciprocal hopping is such a hopping that the right-going and
left-going hopping amplitude are different[25]}. It makes a system
non-Hermitian.
